1. Field
The present disclosure relates to a peer-to-peer communication method in a content centric network environment.
2. Description of Related Art
A current host-based Internet structure has limitations in terms of scalability, security, and network flexibility. In order to overcome these limitations, next Internet, in particular, research on content centric network (hereinafter referred to as a “CCN”) has been actively underway. In a current Internet transmission method, an Internet protocol (IP) address of a sending/receiving host is used to provide services and as much the same data as the number of users is repeatedly transmitted, which results in inefficiency. On the other hand, a CCN uses a content name instead of the IP address to distribute data over the network and thus it is possible to provide a rapid service without repeated transmission of the same data.
FIG. 1 is a diagram illustrating a fundamental operation of the CCN. In the CCN that has been drawing attention recently, it is possible to essentially distribute content using an one-to-many multicast method. Therefore, an efficient content request and distribution is performed when a content source is known. Hereinafter, a content request and distribution method in the CCN will be described with reference to FIG. 1. First, a user transmits a content request message (for example, an interest packet) toward a CCN router using a name of desired content. The CCN router includes a pending interest table (hereinafter referred to as a “PIT”), a content store (CS), and a forwarding information base (FIB) module. The PIT guides interest aggregation and a content data delivery path. When the CCN router receives content data, the CS stores the content data as a cache. The FIB functions as a routing table that is used to determine an interface for delivering a packet from the content name.
The CCN router checks a content name in an interest packet and delivers the interest packet to a source direction of corresponding content. In this case, the CCN router delivers an interest packet of the same content once upward for a predetermined time, and then adds only information on an interface in which the interest packet is received to the PIT. That is, as illustrated in FIG. 1A, when a plurality of users request the same popular content at the same time, routers (R3, R5, R6, R1, R2, and R0) included in the CCN deliver the interest packet only once toward a content server (YouTube). When the interest packet is delivered to the content server, the content server distributes the content reversely to a path from which the interest packet is delivered, as illustrated in FIG. 1B. Since the CCN router stores information on the interface in which the interest packet is received in the PIT, it is possible to deliver data to all interfaces in which the interest packet is received with reference to the PIT when corresponding content data is received. Therefore, in the CCN, it is possible to request and receive data using only a desired content name through the PIT without exchanging location information of source and destination nodes as in an IP network. In addition, the CCN router copies the data in a content storage, and thus it is possible to provide a data service immediately upon receiving a re-request later.